Introduction to The LTPP Information Management System (IMS)

14.1 DATA RELEASE POLICY

The following principles apply for release of LTPP data and information :

LTPP data and information are distributed under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for its contents or use.

Understanding LTPP data collection procedures, principles, and practices is the responsibility of data users who interpret and draw conclusions based on LTPP data and information.

While the LTPP program strives to provide data and information at no cost to the data user, program-funding limitations may limit the level of effort spent on user requests.

Extractions from the LTPP database are provided free of charge to data users who request data in standard data release formats.

Custom extractions from the database may be requested.

Delivery of data in raw data collection formats, access to internal documents, and access to other LTPP offline information will be assessed on a case-by-case basis.

Some LTPP publications are available for free download from the LTPP Internet Web site.

14.2 OBTAINING LTPP DATA

All requests for LTPP data and information should be made to the LTPP customer service center. LTPP customer service can be contacted via e-mail at ltppinfo@fhwa.dot.gov. Other contact information is posted on the LTPP Internet Web page.

LTPP data can be obtained through a variety of mechanisms, including standard data release, custom data extraction, and via the DataPave computer program and the Internet.

14.2.1 Standard Data Release

The most up-to-date data from the LTPP program are distributed in January and July in the standard data release format. These data are available free of charge to data requesters. No data restrictions are placed on the content of the data provided in the tables included in the release. The released tables include all data at all levels of RECORD_STATUS.

The standard data release is currently formatted as a series of Microsoft Access 2000 databases based on the North American software version. In the standard release, the pavement performance database is divided into multiple databases by data module. FWD and profile data modules are subdivided by highway agency to meet Microsoft Access database size limitations. The standard data release is currently formatted on five CD-ROMs. The first volume contains the majority of the data modules, while the other compact discs contain the subdivided FWD and profile data sets.

Use of the standard data release requires knowledge of relational database concepts, the relational design of the LTPP database, and features of the Microsoft Access software. Users of the standard release have the flexibility of performing both simple and complex joins between data elements stored in related data tables to create analysis data sets for many types of pavement performance analyses. Appendix C provides examples of how to extract and create an analysis database that can be conveniently queried by exporting tables from the distribution database files.

The structure of the standard data release format also allows users not familiar with the relational database concept to look at the data in separate tables from a spreadsheet viewpoint. Each table is formatted in columns and rows just like an electronic spreadsheet. This self-discovery feature facilitates progression of use of the expanded data manipulation functions offered by database software that is not available in some spreadsheet types of computational software.

LTPP Database Tip!

Because of the volume of LTPP data, LTPP database users should use modern database tools to examine, manipulate, and extract data. Some tables contain more than 1,000,000 records. LTPP customer service can provide limited technical assistance to database users on the use of these tools.

14.2.2 Custom Extractions

Data users can request partial extractions from the database and/or extractions in a nonstandard format. The support and availability of custom data extractions will be evaluated on a case-by-case basis. While users are encouraged to use the standard data release format, database extractions can be conveniently provided in ASCII, comma-delimited ASCII, or Microsoft Excel 2000 formats. Users interested in obtaining data in other formats must contact the LTPP customer service center.

14.2.3 DataPave

The LTPP DataPave program provides a static release of data from a majority of tables in a user-interactive format. The current version of the program is stored on two CD-ROMs and includes only data whose RECORD_STATUS equals E].

DataPave was designed as a training tool for users of LTPP data who are not acquainted with the use of modern database technology. Since it currently contains program modules based on a static data release, it is not possible to provide data updates to the program without a new release. The most current LTPP data can be obtained from the LTPP standard data release, which is updated every 6 months.

14.2.4 LTPP Data Over the Internet

Plans are underway to make LTPP data available for download over the Internet. Check the LTPP Web page for information on data availability over the Internet.